There are no heat stable milk products especially suitable for cooking or boiling on the market. Today, there is a great interest, need and demand in cookery for heat stable consumer-friendly milk products.
When milk or milk-based food is cooked in a saucepan on a stove, they easily burn on the bottom of the saucepan, causing a burnt flavour to the food and complicating the cleaning of the cookware. Also, an unpleasant film is formed on the surface of the cooked milk. The problem becomes apparent especially in households, where food is cooked on stoves and the temperature of the inner bottom of the saucepan rises high. The problem can be avoided or alleviated to some extent by specially coated cookware, for example. The equipment in institutional kitchens is designed so that the problem of scorching does not usually exist.
During cooking, food ingredients are usually heated in a cookware, saucepan, frying pan or the like on a hot stove. The heat from the stove is transmitted to the cookware and further to the food by conduction. In this type of cooking method, the temperature of the cookware bottom may be much higher than 100° C., i.e. considerably higher than the desirable food temperature. This means that food which is in long-term contact with the cookware bottom is subjected to a very high thermal load. Many foodstuffs cannot withstand the heat of the cookware bottom but stick and scorch onto the bottom of the cookware. In everyday life, food is said to burn on the bottom.
Scorching is harmful for many reasons. Burnt foodstuff causes unpleasant off-flavours, such as a burnt flavour when evaluated organoleptically, appearance defects, such as an untypical colour, and textural faults, such as detached, burnt black constituents, flakiness, precipitates, crust, burnt particles, to the food portion. Scorching of foodstuffs also complicates the cleaning of cookware and utensils. It is laborious to wash away the burnt foodstuff that has stuck tightly onto the bottom. As a result of scorching, the nutritional value of the foodstuff also mainly deteriorates. In addition, combustion products detrimental to health may also be formed.
It is known that scorching can be avoided by different cooking methods, such as heating in water bath, whereby the temperature of the cookware bottom does not rise above the boiling point of water but, on the other hand, heating takes a considerably longer time. Also, it is useful to stir the food actively, which shortens the time the foodstuff is in contact with the bottom. Scorching can also be avoided by cooking equipment, such as by means of a coated cookware (e.g. Teflon). In these cases, foodstuffs do not stick tightly to the bottom of cookware, such as a saucepan, but the scorching as such cannot be entirely avoided.
The sensitivity of foodstuffs to scorching varies a lot. It is well-known that milk or a milk-containing product is a foodstuff that easily burns on the bottom. The scorched matter mainly consists of protein, since proteins and, among milk proteins, whey proteins in particular are the most heat-sensitive substances of foodstuffs. Certain minerals may also affect the scorching phenomenon. There is a need for new solutions and more efficient methods focusing particularly on a milk raw material, which reduce or eliminate scorching and thus minimize the problems associated with heat treatments.
It is also well-known that skim milk or low-fat milk is more sensitive to scorching than whole milk. Consequently, the tendency of milk to burn on the bottom has been avoided by selecting fat-containing milks, such as whole milk, for cooking. According to today's nutrition recommendations, however, skim milk or at least low-fat milk should be used, which causes problems in cooking.
Milk contains many different proteins, the heat sensitivity of which varies considerably. Milk proteins, the portion of which in milk is about 3.3%, are divided into caseins and whey proteins. 20% of milk proteins are whey proteins, the rest are caseins. Caseins are not particularly sensitive to heat. The two largest components in whey proteins are β-lactoglobulin (β-lg) and α-lactalbumin (α-la). Particularly β-lactablogulin is heat-sensitive during a heat treatment.
As is known, milk proteins and particularly whey proteins can be removed from milk in various ways. By using micro- and ultrafiltration techniques and combinations thereof, heat-sensitive whey proteins and the obtained casein dispersion can be removed from a milk raw material and used for cheese production (Schreiber, R., Heat-induced modifications in casein dispersions affecting their rennetability, Intern. Dairy J., 11:2001, 553-558; Kulozik, U. and Kersten, M., New Ways for the Fractionation of Dairy and Minor Constituents Using UTP-Membrane Technology, Bulletin IDF 374:2002, 37-42; Heino, A. et al., Microfiltration of milk I: Cheese milk modification by micro- and ultrafiltration and the effect of Emmental cheese quality, Milchwissenschaft 63 (3) 2008: 279-282; Outinen, M. et al., Microfiltration of milk II: Influence of the concentration factor on the composition of Emmental cheese milk and the κ-casein macropeptide content of the whey, Milchwissenschaft 63 (3) 2008: 305-308).
Furthermore, WO publication 96/08155 describes the changing of the ratio of whey to casein by a micro- and ultrafiltration technique, whereby the obtained fractions may be used for cheese production.
Retail trade and consumers want to have milk products with a flawless flavour, appearance and texture and which withstand heating and high cooking temperatures and whose taste, appearance or texture do not change during the heating either. It is very challenging to achieve products with an absolutely flawless flavour, appearance and texture and which fulfil consumers' expectations on an unscorching milk product and have been manufactured simply and economically. It is an object of the invention to achieve milk-based products which satisfy these demands.